A Great Field Season for Whales!

One of the highlights on my recent field season at Palmer Station was the frequent sightings of whales. In most instances these were either Minke or Humpback Whales, the latter, with its characteristic 3 m high bushy blow, being particularly abundant this season.

There is a certain visceral excitement that permeates the station when an “all call” goes out that “whales had been sighted” just off the station. Many folks drop what they were doing and quickly grab binoculars or cameras to try and get a good view of a dorsal fin or tail as they meander by.

If you are really lucky, whales are sighted while you are out in a zodiac boat. And with a little practive you can navigate the zodiac to a position a good distance in front of the whales and quietly wait so as to not alter their behavior. This sometimes, but not always, results in the whales swimming by relatively close.

Even better, is when the humpbacks decide to slow down from their 15-20 mph swimming speed (generated by huge 20 foot long pectoral fins!) and visit for a while. When this happens there is a cacophony of ooohhhhsss and aaahhhhsss uttered from those on board, coupled with the rapid repetitive sounds of camera shutters.

One day a couple of years ago, I was treated to several humpback whales feeding near Cormorant Island. Humpback whales belong to a group of whales known as baleen whales, characterized by the presence of fibrous sieve-like plates or “baleens” that allow these massive leviathans to gulp and filter out a diet of planktonic organisms living in the sea. The baleens of humpbacks are 3 feet long!

In Antarctica, their diet is comprised primarily of krill, the abundant swarms of shrimp-like animals that comprise the most important food source for higher Antarctic marine predators including penguins, seals, and whales. Amazingly, krill have been estimated to have a biomass that far exceeds that of humans on the planet. Good thing too, as humpback whales, attaining up to 25-30 tons when full grown, require a diet of up to 1000 pounds of krill a day.

Humpback whales are cosmopolitan, occurring in all the major oceans. However, the brunt of their current population, estimated at 30,000 to 40,000 individuals, is found in the southern hemisphere. Having once numbered closer to 100,000 individuals, they continue to recover from heavy hunting up until 1964, when laws were passed to protect them from future exploitation.

This hunting ban was important as their reproductive rates are quite low. For example, humpbacks do not become sexually mature until an age of 6-10 years, and females, which reproduce every two years or so, give birth of a calf about 15 feet long and weighing 1-2 tons. Now that is one big baby!

With continued protection, humpbacks will become even more common along the coastlines of Antarctica, indicative of a recovering ecosystem and generating many more ooohhhhs and aaahhhhhsss for years to come!

Comments

Re: A Great Field Season for Whales!

Posted by
Jeff
on
04/23/07

Have you ever seen Humpbacks using bubble netting to catch krill?

Posted by
Jim
on
04/24/07

Jeff - Great question! While I have never personally seen this remarkable behavior that involves releasing air from the mouth to form curtains of bubbles to concentrate and trap krill swarms, I am well aware that it occurs! Hope that someday I get the chance to see this technique of krill catpure in action!